In the field of photoplethysmography light corresponding with two or more different centered wavelengths may be employed to non-invasively determine various blood analyte concentrations. For example, blood oxygen saturation (SpO2) levels of a patient's blood may be monitored in pulse oximetry systems by measuring the absorption of oxyhemoglobin and reduced hemoglobin using red and infrared light. The measured absorption data allows for the determination of the relative concentration of reduced hemoglobin and oxyhemoglobin, and therefore SpO2 levels, since reduced hemoglobin absorbs more light than oxyhemoglobin in the red band and oxyhemoglobin absorbs more light than reduced hemoglobin in the infrared band; and since the absorption relationships of the two analytes in the red and infrared bands are known. See e.g., U.S. Pat. Nos. 5,934,277 and 5,842,979.
As may be appreciated, in order to accurately compute blood analyte concentrations, it is important for pulse oximetry systems to be preset, or “calibrated”, in relation to the center wavelengths of red and infrared light employed. In this regard, pulse oximetry arrangements typically comprise a disposable or reusable sensor that is releasably attached to a given patient's appendage (e.g., finger, ear lobe, infant foot or nasal septum) for a given patient monitoring procedure. The sensor carries at least one red light source and one infrared light source, as well a light detector to provide an output signal indicative of the light received thereby (e.g. the red and infrared light passing through the patient appendage). In turn, the sensor may be connected or selectively interconnectable to a cable that is selectively interconnectable to a photoplethysmographic monitor to process the detector output signals.
Given such selective interconnections, a number of approaches have been developed for identifying a given sensor to an interconnected photoplethysmographic monitor so as to insure compatibility (e.g. so that the monitor may process the sensor detector output signal based upon assumed or calibrated values, or algorithms, reflective of the center wavelength(s) of the interconnected sensor light source(s)). Such known approaches largely entail the utilization of dedicated sensor componentry and corresponding cable connections, thereby adding cost, complexity and mass. Further, many of the known approaches raise reliability concerns since the identifying componentry can be easily implemented by sensor suppliers offering sensors that do not otherwise satisfy performance parameters established for accurate measurements by and/or effective use of a given interconnectable monitor.